R-38 low slope, vented roof Charlotte, NC.
I’ve read the article about this here, but it is more about blown in or batt insulation. https://www.greenbuildingadvisor.com/article/insulating-low-slope-residential-roofs
I am adding a 16×32′ addition to the back of my house and to keep the costs down I want to have a monoslope , low slope roof which is about 10′ at the high end and goes down to about 9′ at the low end. by the time I add 10″ of ceiling insulation and 4″ of floor insulation I will be 7′ 10″ height at the low end.
I can either use traditional 2×10 rafters: TPO membrane roof, OSB, then 1.5″ air gap then 8″ of 2″ Poly iso boards which will have thermal bridging
OR i can use steel stud rafters which are only 6″ tall. however I am having trouble visualizing how I would layer the insulation and still have an air gap with this approach. seems like I would have to screw a 2×4 on top of the 2×6 metal rafter so I could attach the OSB to the rafters. therefore the 2×4 would thermal bridge to the 2×6 and thermal bridging woudl still be an issue?
is there a better way to go about this? is there a water proof alternative to osb so I wont’ have to worry about mold/condensation? how about painting the osb with copper coat green anti microbial before installing?
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